Text

theses

High tunnels with polyethylene plastic film are often used by farmers for season extension. Previous research has suggested the possible migration of volatile organic chemical compounds (VOCs), including formaldehyde, from polyethylene film to surface/ground dust or soil and to the air. The current Safety Data Sheet (Shanghai Hitec Plastics, 2012) for polyethylene film documented that carbon dioxide may also be released under certain conditions of direct sunlight, heat (air temperature) and/or higher relative humidity.

Release of and exposure to formaldehyde and carbon dioxide may lead to negative health and environmental impacts. Exposures can also trigger asthma symptom episodes or other respiratory issues. According to National Institute of Health’s (NIH) National Cancer Institute (NCI) short-term exposure to formaldehyde levels in air exceeding 0.1 parts per million (ppm) may cause adverse events in some individuals, including watering and burning eyes, irritation of the nose and throat, coughing, respiratory issues such as wheezing, nausea, and skin irritation (NIH NCI, 2011). Exposure to higher levels of formaldehyde may cause some types of cancers. In 2011 the Department of Health and Human Services (DHHS) defined formaldehyde as a known human carcinogen (ATSDR, 2015). The United States Environmental Protection Agency (EPA) considers formaldehyde to be a probable human cancer-causing agent (2016). The United States EPA is currently revising its assessment of formaldehyde to address the DHHS 2011 recommendations (EPA, 2017a). According to the International Agency for Research on Cancer (IARC), based on animal toxicological and human epidemiological studies, formaldehyde is classified as a carcinogen to humans (2018). Carbon dioxide release not only contributes to the overall environmental impacts as a known greenhouse gas implicated in climate change (EPA, 2017b), but it is also an indicator of ventilation (inside buildings and in semi-enclosed areas) and a component of the emissions from polyethylene film (Shanghai Hitec Plastics, 2012). Air sampling can therefore identify the impact of polyethylene film on indoor (inside a high tunnel) air and environmental quality.

This pilot case study characterized a modern-day high tunnel covered with a Sunmaster® IV polyethylene film and critically examined potential polyethylene film emissions. In this study, sampling and analysis were conducted for exposures to formaldehyde and carbon dioxide from a new high tunnel covered with Sunmaster® IV polyethylene film. Indoor and outdoor sampling and analysis were conducted for exposures to formaldehyde from the use of new Sunmaster® IV polyethylene plastic film for a Rimol Nor’Easter high tunnel set-up and commissioned on a rural organic farm in western Maryland for six weeks from early June 2017 to mid-July 2017. Concurrently, continuous sampling of carbon dioxide, air temperature and relative humidity was performed for a total of 12 weeks from early June 2017 to mid-July 2017 (summer season) and September 2017 to November 2017 (fall season).

Formaldehyde concentrations above outdoor background levels were detected. However, none of the measured indoor air or indoor air minus outdoor air concentrations of formaldehyde exceeded existing federal and state agency reference guidelines limits (OSHA, 2018a). In addition, indoor carbon dioxide levels were measured at above outdoor ambient levels with some samples near or exceeding indoor air quality guidelines (ASHRAE, 2013). This could possibly be due to poor ventilation and emissions from the polyethylene film. Sunny conditions led to higher indoor air temperatures during the summer sampling season. Summer season indoor mean relative humidity was lower than outdoor mean relative humidity. However, during the fall sampling season, indoor mean relative humidity was higher than outdoor mean relative humidity.

High tunnels covered with Sunmaster® IV polyethylene film unlikely present public health concerns if initially constructed and properly commissioned with adequate ventilation typically used in commercial growing settings on rural farms like in this study, or in urban areas, e.g., repurposed open lots.

Characterization of polyethylene film emissions was important to ensure a healthy working environment inside high tunnels and for protection of natural resources; improvement of the quality of life for farmers, and the agriculturalcommunity; and, to support agricultural sustainability.

ETD_9188

doi:10.7282/T34X5CDG

Ph.D.

Includes bibliographical references

by Mehra Bahremand Blott

ETD doctoral

The author owns the copyright to this work.